CVE-2026-90160 (GCVE-0-2026-90160)
Vulnerability from cvelistv5
Published
2026-09-17 16:06
Modified
2026-10-19 08:58
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: lwt_bpf: Restore reserved headroom after xmit program ip_finish_output2() expands an skb to LL_RESERVED_SPACE(dev) before LWT xmit. An LWT_XMIT BPF program can then modify the skb head and still return BPF_OK, so bpf_xmit() rechecks the remaining headroom before the skb continues to neighbour output. That recheck uses dst->dev->hard_header_len. This is not enough for the neighbour cached-header path: neigh_hh_output() copies the cached hardware header using the aligned hh_cache size, HH_DATA_MOD for short headers or HH_DATA_ALIGN(hh_len) otherwise. On Ethernet, hard_header_len is 14 but the cached copy needs 16 bytes. If an LWT_XMIT BPF program calls bpf_skb_change_head(skb, 1, 0), the skb can still have 15 bytes of headroom after the program. The existing check accepts that, after which neigh_hh_output() hits its headroom warning and drops the skb. Use LL_RESERVED_SPACE(dst->dev) in the post-BPF headroom check to match the reservation made before LWT xmit.
References
Impacted products
Vendor Product Version
Linux Linux Version: 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2
Version: 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2
Version: 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2
Version: 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2
Version: 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2
Version: 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2
Version: 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2
Version: 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/core/lwt_bpf.c"
          ],
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          "vendor": "Linux",
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.10"
            },
            {
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              "version": "0",
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            },
            {
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              "version": "5.10.270",
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            },
            {
              "lessThanOrEqual": "5.15.*",
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              "version": "5.15.221",
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            {
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            {
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              "lessThanOrEqual": "*",
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              "versionType": "original_commit_for_fix"
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      ],
      "cpeApplicability": [
        {
          "nodes": [
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              "cpeMatch": [
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nlwt_bpf: Restore reserved headroom after xmit program\n\nip_finish_output2() expands an skb to LL_RESERVED_SPACE(dev) before LWT\nxmit. An LWT_XMIT BPF program can then modify the skb head and still\nreturn BPF_OK, so bpf_xmit() rechecks the remaining headroom before the\nskb continues to neighbour output.\n\nThat recheck uses dst-\u003edev-\u003ehard_header_len. This is not enough for the\nneighbour cached-header path: neigh_hh_output() copies the cached hardware\nheader using the aligned hh_cache size, HH_DATA_MOD for short headers or\nHH_DATA_ALIGN(hh_len) otherwise.\n\nOn Ethernet, hard_header_len is 14 but the cached copy needs 16 bytes. If\nan LWT_XMIT BPF program calls bpf_skb_change_head(skb, 1, 0), the skb can\nstill have 15 bytes of headroom after the program. The existing check\naccepts that, after which neigh_hh_output() hits its headroom warning and\ndrops the skb.\n\nUse LL_RESERVED_SPACE(dst-\u003edev) in the post-BPF headroom check to match\nthe reservation made before LWT xmit."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:58:58.842Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/753e5cdcca5474d230d62bb3489e5168ab27c272"
        },
        {
          "url": "https://git.kernel.org/stable/c/c488071c3441fa34f5a87cd6c12ce2cc6304f20e"
        },
        {
          "url": "https://git.kernel.org/stable/c/a38c0eb447e2dd0120a2ebcdba470f9505ac8907"
        },
        {
          "url": "https://git.kernel.org/stable/c/de2b2004e16f2930eb689175e2c1998b0a68d499"
        },
        {
          "url": "https://git.kernel.org/stable/c/7d043e24520a273c362be5dd7d9c82796879a49b"
        },
        {
          "url": "https://git.kernel.org/stable/c/7cf561843ed0ad57501892a65abb77957e6c800f"
        },
        {
          "url": "https://git.kernel.org/stable/c/179a5b2171573d94a25c9aa8e1c9f9ac352ad316"
        },
        {
          "url": "https://git.kernel.org/stable/c/5fe7007aed9ad069b2bd77e5d0c875c64f5c0269"
        }
      ],
      "title": "lwt_bpf: Restore reserved headroom after xmit program",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90160",
    "datePublished": "2026-09-17T16:06:51.806Z",
    "dateReserved": "2026-09-11T19:38:34.790Z",
    "dateUpdated": "2026-10-19T08:58:58.842Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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